This invention relates generally to control of power and more specifically to peak power regulation.
The use of Code Division Multiple Access (CDMA) technology is increasing within wireless applications such as cellular and Personal Communication Systems (PCS). Its utilization will continue to be significant as CDMA technology is incorporated within new standards such as the third generation (3G) Direct Spreading (DS)-CDMA communication system currently being defined. In CDMA technologies, multiple users and/or multiple data streams of each user, which each transmit information on a different code channel, share the same frequency channel, hereinafter referred to as a carrier. Furthermore, CDMA transmitters may also utilize multiple carriers, and therefore, multiple CDMA carriers share the same power amplifier and other components within a particular transmitter. This sharing of carriers between users and/or the sharing of power amplifiers and other components between carriers cause compounded signals to have a high Peak to Average Power Ratio (PAPR) to be processed by said components. In the 3G DS-CDMA standards, multiple code channels share the same carrier within 3G mobile stations. Hence, similar to that for a base station, compounded signals with potentially high PAPR are input to the power amplifiers of 3G mobile stations.
In order to meet the out-of-band emissions requirements, a power amplifier and other components with this high PAPR input is required to provide good linearity in a large dynamic range. This makes the power amplifier one of the most expensive components within the communication system. The high PAPR also means that the power amplifier operation has low power efficiency. When considering the 3G DS-CDMA case, this low power efficiency reduces the battery life time for 3G mobile stations.
An apparatus is thus needed that can reduce the PAPR of CDMA signals input to power amplifiers. Such a device should reduce the peaks of the compounded input signals such that a less expensive power amplifier can be utilized with out-of-band emissions still being fully controlled. This device should also be relatively inexpensive and any degradation in terms of in-band signal quality should be within an acceptable range.
It is an object of the present invention to overcome the disadvantages of the prior art and, in particular, to provide an apparatus whereby the Peak to Average Power Ratio (PAPR) within a signal is controlled.
According to a first broad aspect, the present invention provides a peak power regulator, input with at least one input signal, that outputs at least one output signal corresponding to the input signal, the power regulator comprising: a delay apparatus that generates a delayed signal corresponding to the input signal; a power estimation apparatus that generates, with use of the input signal, an overall input power estimation signal corresponding to the input signal; a scaling factor generator that generates a scaling factor with use of the overall input power estimation signal and a maximum acceptable power signal; a power scaling apparatus that utilizes the scaling factor and the delayed signal to generate a scaled signal corresponding to the output signal; and a filtering apparatus that filters the scaled signal to generate the output signal.
According to a second broad aspect, the present invention provides an envelope magnitude regulator, input with at least one IF input signal, that outputs at least one IF output signal corresponding to the IF input signal, the envelope magnitude regulator comprising: a delay apparatus that generates a delayed IF signal corresponding to the IF input signal; an envelope magnitude estimation apparatus that generates, with use of the IF input signal, an overall input envelope magnitude estimation signal corresponding to the IF input signal; a scaling factor generator that generates a scaling factor with use of the overall input envelope magnitude estimation signal and a maximum acceptable envelope magnitude signal; an envelope magnitude scaling apparatus that utilizes the scaling factor and the delayed IF signal to generate a scaled IF signal corresponding to the IF output signal; and a filtering apparatus that filters the scaled IF signal to generate the IF output signal.
According to a third broad aspect, the present invention provides In a peak power regulator, input with at least one input signal, that outputs at least one output signal corresponding to the input signal, a method for regulating output power comprising the steps of: estimating the overall input power level corresponding to the input signal; generating a scaling factor with use of the estimate of the overall input power level and a maximum acceptable input power signal; delaying the input signal; generating a scaled signal corresponding to the output signal with use of the scaling factor and the delayed input signal; and filtering the scaled signal to generate the output signal.